The present research is designed to determine whether or not cases of Hodgkin's Disease (HD) aggregate through prior interpersonal contact prior to their disease manifestation more than would be expected to occur by change in comparable persons without the disease and, if so, whether such "exposure-clustering" is confined to young persons under age 40. Although epidemiologic and clinical findings suggest that HD may be the result of two etiologic processes, that in the young perhaps being of an infectious origin, no adequate demonstration of space-time aggregations of HD cases has yet been observed. Similarly, several specific factors which bear on the hypothesis of an infectious etiology have not yet been evaluated and the effects of additional purported risk factors are not well understood. This study employs a matched-pair case-control design, which is a new approach in searching for aggregations of HD cases through prior contact and assessing the significance of those contacts found. It also provides the opportunity to more fully assess several potential factors of risk for the disease. Approximately 250 cases of HD are to be identified in three Western Washington counties using a population-based cancer registration system, and one control is chosen for each case of the same sex and approximate age from the case's neighborhood of residence at the time of his/her diagnosis. Data collected through personal interviews will be analyzed using newly-developed techniques to look for excessive prior contact among cases. In addition, evaluations will be made of the following factors, many of which may bear on an infectious model of disease: 1) childhood social class, birth order, family size and common infections; 2) exposures to drugs, especially amphetamines and narcotics; 3) exposure to sick domestic animals; 4) exposure to phytohemagglutinin (PHA); 5) prior surgery, especially tonsillectomy and appendectomy; 6) prior infectious mononucleosis; 7) seasonality of date of first symptom; and 8) occupational exposure to wood or wood products.